When bulk materials contact the ambient environment, they are subject to oxidative deterioration because of contact with oxygen and air. Such oxidative deterioration can have many negative effects. For example, when a solid fuel material, such as coal, is being transported from a mine to a utility or is in storage at a utility, it is subject to oxidation. One negative aspect of such oxidative deterioration is a loss in the thermal value of the coal. Depending upon the type of coal and its water content, among other factors, between 1% and 5% of the thermal value of coal can be lost from the time it is mined until the time at which it is consumed. These losses are sizeable in the domestic United States utility industry, which consumes about 800 million tons of coal per year. Such losses are particularly significant for low rank coals such as lignite and sub-bituminous coals, especially for such materials which have been upgraded by thermal treatment to reduce moisture. Moreover, low level oxidation of coal generates heat. As a result, there is a significant risk of certain coal materials self-igniting, resulting in a risk to property and life.
Most efforts to reduce oxidative deterioration have focused on reducing the risk of self-heating and thereby self-ignition of coals. The problem has been addressed by a variety of approaches. One such approach is by compacting coal as it is transported or stored. By compacting coal, the surface area of the coal that is in contact with the ambient environment can be reduced. Such a reduction of surface area contact reduces the amount of coal available for oxidation by the ambient environment. Another approach has been to flatten and trim coal piles to decrease the ability of the coal pile to hold heat and therefore generate enough heat through self-heating to self-ignite. In addition, contacting coal materials with various fluids, such as hydrocarbon based materials, has been used.
While the more chronic problem of loss of economic value of bulk materials, such as the loss of heating values in coal, has been recognized and studied, adequate widespread use of strategies for significantly reducing economic losses from this problem have not been achieved. Therefore, a need exists for reducing the oxidative deterioration of bulk materials.